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<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        const promise1 = new Promise((resolve,reject)=>{
            console.log('promise1')
            resolve('resolve') // 立刻 第一个宏任务 pending -> fulfilled
        })
        // promise1.then 的返回值还是promise
        const promise2 =promise1.then(res =>{
            console.log(res)
            return new Promise((resolve,reject) =>{
                resolve()
                console.log(promise2,'========')
            })
        })
        console.log(promise2,'-----------')
        console.log(1, promise1) // 1 Promise{fulfilled}
        console.log(2, promise2) // 2 Promise{pending}
    </script>
</body>
</html>